How to market yourself as a gigging singer

You must phone local agents, anyone can find these numbers online and call them asking to do a showcase. Then really think about putting together usually 20 min spot to showcase what you can do. Take all relevant paperwork with you, full set list, posters, or publicity photos they can use for different venues and most importantly your availability (date sheet)
Plan your outfit carefully and never arrive to a showcase wearing what you will go on stage wearing, always sets a good impression if you ask where to get changed. Also in doing this you will be setting your own standards to be doing the wonderful working men's clubs all over the country instead of the back street pubs where you get changed in a dressing toilet with cold feet on the tiled floor and propping your bag against the door because someone has kicked the door in and broken the lock.
There are many venues that also hold open mike nights this is a great opportunity to take part try new material and see how it goes down with the crowds, don't forget you are performing for and entertaining your audience. You have to play / sing what they want to hear, usually human, sex on fire or simply the best for a drunken Saturday night finale.
At any opportunity take footage of your performances and post them on youtube this builds your viral portfolio and makes you more accessible via the World Wide Web. I had a friend of mine set me up a website, it's only £40 a year and you can do all this yourself. Don't go spending thousands of pounds on a website you have to think logically and if when you've started doing the little jobs and start making a lot of money doing more corporate work ect.. Maybe then upgrade to a higher standard website. But when your just starting out, keep things simple.